It is generally desirable to know whether a temperature-sensitive good, at any point in time, has been subjected to an undesirable temperature, and thus may have been damaged.
It would also be desirable to know at what point in time the good was subjected to such undesirable temperature, such that measures may be taken to prevent such undesirable temperatures in the future, or such that responsibility may be allocated.
It would also be desirable to know for how long time the good was subjected to such undesirable temperature.
With such additional knowledge, it would be possible to determine, with greater accuracy, whether the good has actually been damaged or not.
A frequently occurring type of goods that would be desirable to monitor, is groceries, in particular groceries that are to be kept cold or frozen. However, as many groceries are produced in large volumes and are subject to cost restraints, a suitable monitoring device would need to be capable of being produced at a low cost.
U.S. Pat. No. 4,929,090 A discloses a device that is to be attached to objects, such as groceries, for recording what temperatures the object has been subjected to. The device comprises multiple electrode sets interacting with an electrolyte. Temperature sensors are arranged to complete an electrical circuit including two electrodes at a predetermined temperature. The device disclosed in U.S. Pat. No. 4,929,090 A is, however, relatively complex, and it is unlikely that this device can be produced at a sufficiently low cost.
U.S. Pat. No. 6,198,701 B1 discloses an electrochemical timer for use with groceries, involving electrodes and an electrolyte. Consumption of one of the electrodes enables measuring the time. The device of U.S. Pat. No. 6,198,701 B1 does not provide any knowledge of what temperatures the good has been subjected to.
U.S. Pat. No. 4,804,275 A discloses an indicator device for indicating the time integral of a monitored parameter. However, the device of U.S. Pat. No. 4,804,275 A does not provide any information as to when the monitored object was subjected to a particular temperature, or for how long.
GB 903,967 A discloses an indicator for temperature history of a frozen grocery, wherein the electrolytic action is temperature-dependent, with substantially no electrolytic action taking place below a predetermined temperature level. Hence, the device of GB 903,967 A is only capable of indicating the time integral of the temperature for the period when the predetermined temperature was superseded. Hence, the device of GB 903,967 A also does not provide any indication of when the monitored object was subjected to a particular temperature.
EP 0 735 368 A1 discloses a method for monitoring an accumulated value of temperature and time. The method involves contacting an oxidation-polymerizable dyestuff and an oxidation agent, the reaction between which being controlled by time and temperature. Hence, the method of EP 0 735 368 A1 also does not provide any indication of when the monitored object was subjected to a particular temperature.
Hence, there is a need for an improved device for monitoring a parameter history.